Association of PIK3CG gene polymorphisms with attention-deficit/hyperactivity disorder: A case-control study.

Attention-deficit/hyperactivity disorder (ADHD) is a complicated neurodevelopmental disorder with high heritability. This study explores the association of PIK3CG gene single nucleotide polymorphisms (rs1129293, rs12536620, rs12667819, rs17847825, rs2230460) with ADHD in children and the relation of interaction between SNPs and environmental factors, including blood lead levels (BLLs) and feeding style. A case-control study was conducted with children aged 6-18years old, consisting of 389 children newly diagnosed with ADHD via the DSM-IV at the Wuhan Women and Children Medical Care Center, and 393 control participants were healthy children for physical examination during the same period. All participants were tested using the Chinese Wechsler Intelligence Scale for Children and Parent Symptom Questionnaire (PSQ). Furthermore, a self-designed questionnaire was used to investigate the general situation and related environmental factors, and the BLLs were measured by atomic absorption spectrophotometry. The genotyping was performed using Sequenom MassArray. In our study, PIK3CG gene rs12667819 was consistently shown to be associated with ADHD risk in dominant model (OR=1.656, 95% CI=1.229-2.232), ADHD-I type (OR=2.278, 95% CI=1.666-4.632), and symptom scores. Moreover, rs12536620 has been observed to be related to ADHD-C type and symptom scores. Intriguingly, gene-environmental interactions analysis consistently revealed the potential interactions of rs12667819 collaborating with blood lead (Pmul=0.045) and feeding style (Pmul=0.041) to modify ADHD risk. Expression quantitative trait loci analysis suggested that rs12667819 may mediate PIK3CG gene expression. Therefore, our results suggest that selected PIK3CG gene variants may have a significant effect on ADHD risk.

SLC6A1 gene involvement in susceptibility to attention-deficit/hyperactivity disorder: A case-control study and gene-environment interaction.

Attention-deficit/hyperactivity disorder (ADHD) is an early onset childhood neurodevelopmental disorder with an estimated heritability of approximately 76%. We conducted a case-control study to explore the role of the SLC6A1 gene in ADHD. The genotypes of eight variants were determined using Sequenom MassARRAY technology. The participants in the study were 302 children with ADHD and 411 controls. ADHD symptoms were assessed using the Conners Parent Symptom Questionnaire. In our study, rs2944366 was consistently shown to be associated with the ADHD risk in the dominant model (odds ratio [OR]=0.554, 95% confidence interval [CI]=0.404-0.760), and nominally associated with Hyperactive index score (P=0.027). In addition, rs1170695 has been found to be associated with the ADHD risk in the addictive model (OR=1.457, 95%CI=1.173-1.809), while rs9990174 was associated with the Hyperactive index score (P=0.010). Intriguingly, gene-environmental interactions analysis consistently revealed the potential interactions of rs1170695 with blood lead (Pmul=0.044) to modify the ADHD risk. Expression quantitative trait loci analysis suggested that these positive single nucleotide polymorphisms (SNPs) may mediate SLC6A1 gene expression. Therefore, our results suggest that selected SLC6A1 gene variants may have a significant effect on the ADHD risk.

Attention-deficit/hyperactivity disorder associated with KChIP1 rs1541665 in Kv channels accessory proteins.

Attention-deficit/hyperactivity disorder (ADHD) is an early onset childhood neurodevelopmental disorder with high heritability. A number of genetic risk factors and environment factors have been implicated in the pathogenesis of ADHD. Genes encoding for subtypes of voltage-dependent K channels (Kv) and accessory proteins to these channels have been identified in genome-wide association studies (GWAS) of ADHD. We conducted a two-stage case-control study to investigate the associations between five key genes (KChIP4, KChIP1, DPP10, FHIT, and KCNC1) and the risk of developing ADHD. In the discovery stage comprising 256 cases and 372 controls, KChIP1 rs1541665 and FHIT rs3772475 were identified; they were further genotyped in the validation stage containing 328cases and 431 controls.KChIP1 rs1541665 showed significant association with a risk of ADHD at both stages, with CC vs TT odds ratio (OR) = 1.961, 95% confidence interval (CI) = 1.366-2.497, in combined analyses (P-FDR = 0.007). Moreover, we also found rs1541665 involvement in ADHD-I subtype (OR (95% CI) = 2.341(1.713, 3.282), and Hyperactive index score (P = 0.005) in combined samples.Intriguingly, gene-environmental interactions analysis consistently revealed the potential interactionsof rs1541665 collaboratingwith maternal stress pregnancy (Pmul = 0.021) and blood lead (Padd = 0.017) to modify ADHD risk. In conclusion, the current study provides evidence that genetic variants of Kv accessory proteins may contribute to the susceptibility of ADHD.Further studies with different ethnicitiesare warranted to produce definitive conclusions.

The Association of SNAP25 Gene Polymorphisms in Attention Deficit/Hyperactivity Disorder: a Systematic Review and Meta-Analysis.

Attention deficit/hyperactivity disorder (ADHD) is one of the most highly heritable psychiatric disorders in childhood. The risk gene mutation accounts for about 60 to 90 % cases. Synaptosomal-associated protein of 25 kDa (SNAP-25) is a presynaptic plasma membrane protein which is expressed highly and specifically in the neuronal cells. A number of evidences have suggested the role of SNAP-25 in the etiology of ADHD. Notably, the animal model of coloboma mouse mutant bears a ∼2-cM deletion encompassing genes including SNAP25 and displays spontaneous hyperkinetic behavior. Previous investigators have reported association between SNPs in SNAP25 and ADHD, and controversial results were observed. In this study, we analyzed the possible association between six polymorphisms (rs3746544, rs363006, rs1051312, rs8636, rs362549, and rs362998) of SNAP25 and ADHD in a pooled sample of ten family-based studies and four case-control studies by using meta-analysis. The combined analysis results were significant only for rs3746544 (P = 0.010) with mild association (odds ratio (OR) = 1.14). And, the meta-analysis data for rs8636, rs362549, and rs362998 are the first time to be reported; however, no positive association was detected. In conclusion, we report some evidence supporting the association of SNAP25 to ADHD. Future research should emphasize genome-wide association studies in more specific subgroups and larger independent samples.

The Physiology of BDNF and Its Relationship with ADHD.

Brain-derived neurotrophic factor (BDNF) is a major neurotrophin in the central nervous system that plays a critical role in the physiological brain functions via its two independent receptors: tropomyosin-related kinase B (TrkB) and p75, especially in the neurodevelopment. Disrupting of BDNF and its downstream signals has been found in many neuropsychological diseases, including attention-deficit hyperactivity disorder (ADHD), a common mental disorder which is prevalent in childhood. Understanding the physiological functions of BDNF during neural development and its potential relationship with ADHD will help us to elucidate the possible mechanisms of ADHD and to develop therapeutic approaches for this disease. In this review, we summarized the important literatures for the physiological functions of BDNF in the neurodevelopment. We also performed an association study on the functional genetic variation of BDNF and ADHD by a case-control study in the Chinese mainland population and revealed the potential correlation between BDNF and ADHD which needs further research to confirm.